An air dryer of the above kind is used, for example on a heavy road vehicle, for drying compressed air delivered from a compressor. The cartridge, here called the main cartridge, may for example contain silica gel with small pores for the drying function, and such a cartridge is available on the market, also as a spare part.
It may, however, be desirable with a more complex treatment of the compressed air for improving its quality, before it is transferred to different consumers, where the air quality is of essence.